The BTM 1200 and 500 series vacuum tube machines were Digital. 
The 500 series were 4 bit hexadecimal with 3 x 24 character registers, 
sterling and square root was handled in in the hardware. 
The vacuum tubes used were predominately 12AU7 twin triodes 
(for flip flops) 6BQ5 power pentodes and 2D21 Thyratrons. 
Programming was via Plug Panels and you had up to 150 "Program Steps"
"to do your job".

The clock rate of the 555 was 14Khz and derived via a magnetic reluctance
pickup from a toothed gear on the 1000 x 4 bit character drum spinning 
at 1500 rpm. The drum was an aluminium cylinder with recording wire 
(as used on WW2 audio wire recorders) wound on the drum for the recording media. 
Each track had separate read, write and erase heads. 
Input and output was limited to 80 column punched cards. 

All BTM/ Hollerith punched card equipment was 80 column. 
The blank cards were produced from imported Swedish card stock for the 
pacific area at a factory in Lexton Road Box Hill. 
This factory was also the Field Engineering training facility for punched 
card equipment (or unit record equipment as IBM liked to call it). 
 
A few items of Hollerith punched card equipment were exact duplicates of 
the IBM equivalent including Collators and Reproducers. 
This was a carry over from the lend lease arrangement that existed 
during WW2 between USA and England. 

Most mechanical parts were interchangeable. 
All Hollerith punched card gear was 110 volt DC derived from a small 240 Volt 
50 HZ MG set except card sorters that used selenium rectifiers.  
All  IBM "Unit Record" equipment was 40 Volt DC. IBM 523 Card punches were used 
on the ABS sites. The Hollerith equivalent was called a 239 only the power 
supply and relays were different.
 
Powers Samas machines (ECC and PCC) were also digital and the programming was 
stored on what looked like a large printed circuit board with programming being
accomplished by inserting and removing pins into the board. 
Input and output was also limited to round hole punched cards. 
The PCC also had a drum.
 
Other than these machines all of their "punched card machines were strictly 
mechanical with the only electrical device being the motor that drove the 
intricate system of levers, Bowden cables and cranks. Truly amazing designs 
considering that all sensing of card holes was done by pins on the end of Bowden 
cables at up to 1000 cards per minute. These machines included card 
punches/verifiers, collators, reproducers, sorters, listers and tabulators. 
They were available for 21, 40, and 80. round holes rather than the IBM/ICL 
rectangular standard. 
AAMOI IBM and Hollerith/ICT used different alpha physical punched card codes.

Ron Bird